Financial Derivatives (Schedule Of Gains And Losses On Derivative Contracts) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Derivative [Line Items]
Net Realized Gain/(Loss)	$ (3,187)	$ 6,404	$ (31,669)	$ 16,877
Change in Net Unrealized Gain/(Loss)	(2,664)	(11,108)	15,015	(18,130)
Financial Derivatives - Assets [Member]
Derivative [Line Items]
Net Realized Gain/(Loss)	2,306	9,904	(11,765)	13,335
Change in Net Unrealized Gain/(Loss)	(7,847)	3,495	(925)	(106)
Financial Derivatives - Assets [Member] | Credit Default Swaps On Asset Backed Securities [Member]
Derivative [Line Items]
Primary risk exposure	Credit	Credit	Credit	Credit
Net Realized Gain/(Loss)	3,963	3,088	(1,514)	8,396
Change in Net Unrealized Gain/(Loss)	(3,823)	(248)	4,285	(4,987)
Financial Derivatives - Assets [Member] | Credit Default Swaps On Asset Backed Indices [Member]
Derivative [Line Items]
Primary risk exposure	Credit	Credit	Credit	Credit
Net Realized Gain/(Loss)	(134)	6,539	(7,200)	5,313
Change in Net Unrealized Gain/(Loss)	(4,174)	3,746	(6,442)	5,719
Financial Derivatives - Assets [Member] | Credit Default Swaps On Corporate Bond Indices [Member]
Derivative [Line Items]
Primary risk exposure	Credit	Credit	Credit	Credit
Net Realized Gain/(Loss)	12	(150)	(1,548)	(150)
Change in Net Unrealized Gain/(Loss)	(602)	109	570	109
Financial Derivatives - Assets [Member] | Total Return Swaps [Member]
Derivative [Line Items]
Primary risk exposure	Equity Market	Equity Market	Equity Market	Equity Market
Net Realized Gain/(Loss)	(1,520)	(29)	(1,520)	(29)
Change in Net Unrealized Gain/(Loss)	257	826	257	826
Financial Derivatives - Assets [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Primary risk exposure	Interest Rates	Interest Rates	Interest Rates	Interest Rates
Net Realized Gain/(Loss)	0	456	49	(195)
Change in Net Unrealized Gain/(Loss)	495	(938)	417	(1,773)
Financial Derivatives - Assets [Member] | Eurodollar Futures [Member]
Derivative [Line Items]
Primary risk exposure	Interest Rates		Interest Rates
Net Realized Gain/(Loss)	(15)		(32)
Change in Net Unrealized Gain/(Loss)	0		(12)
Financial Derivatives - Liabilities [Member]
Derivative [Line Items]
Net Realized Gain/(Loss)	(5,493)	(3,500)	(19,904)	3,542
Change in Net Unrealized Gain/(Loss)	5,183	(14,603)	15,940	(18,024)
Financial Derivatives - Liabilities [Member] | Credit Default Swaps On Asset Backed Indices [Member]
Derivative [Line Items]
Primary risk exposure	Credit	Credit	Credit	Credit
Net Realized Gain/(Loss)	(190)	24	4,372	8,886
Change in Net Unrealized Gain/(Loss)	1,543	(1,038)	650	(1,256)
Financial Derivatives - Liabilities [Member] | Credit Default Swaps On Corporate Bond Indices [Member]
Derivative [Line Items]
Primary risk exposure	Credit	Credit	Credit	Credit
Net Realized Gain/(Loss)	(160)	100	143	0
Change in Net Unrealized Gain/(Loss)	11	220	11	186
Financial Derivatives - Liabilities [Member] | Total Return Swaps [Member]
Derivative [Line Items]
Primary risk exposure	Equity Market		Equity Market
Net Realized Gain/(Loss)	1,066		(2,262)
Change in Net Unrealized Gain/(Loss)	252		273
Financial Derivatives - Liabilities [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Primary risk exposure	Interest Rates	Interest Rates	Interest Rates	Interest Rates
Net Realized Gain/(Loss)	(6,209)	(3,249)	(22,157)	(4,250)
Change in Net Unrealized Gain/(Loss)	3,410	(14,154)	15,093	(17,844)
Financial Derivatives - Liabilities [Member] | Eurodollar Futures [Member]
Derivative [Line Items]
Primary risk exposure	Interest Rates	Interest Rates	Interest Rates	Interest Rates
Net Realized Gain/(Loss)	0	(375)	0	(1,094)
Change in Net Unrealized Gain/(Loss)	$ (33)	$ 369	$ (87)	$ 890